Greatcoat billowing in the breeze, Sherlock stepped gracefully from the rooftop edge on Sunday night and began his plummet towards earth. John Watson watched in horror – and at home 8 million BBC1 viewers did much the same. What was going on? Had the BBC just sacrificed its much-loved consulting detective? The clue was in the already announced third series. But that didn't stop the collective gasp when Sherlock appeared at his own funeral looking decidedly unburied.

So how did he do that? There are no shortage of theories, including the one that he'd turned into an enormous Sherlock-shaped robot spaceship controlled by tiny, tiny people. But most share a few starting points: Sherlock had asked mortician Molly for help; he told John to stand in a certain spot; the kidnapped girl had screamed at Sherlock's face; John was knocked over by a cyclist and was unable to take (a splattered) Sherlock's pulse.

There's some general agreement too that Moriarty might have worn a lifelike Sherlock mask when he kidnapped the children earlier. (Hence the scream.) Nearly everyone thinks that the crowd in the street, the hospital staff and the cyclist were members of Sherlock's homeless network, and that Molly would have falsified the autopsy. So the detective only had to fool John – although that's still some ask.

One popular theory holds that Sherlock didn't jump off the building at all. Instead the corpse of Moriarty, newly dead, was dropped to the ground wearing the Sherlock mask and his nemesis's clothes. Alternatively, Moriarty's body was thrown from the rooftop – variations include using a masked dummy glimpsed in 221B earlier in the episode, or a masked cadaver supplied by Molly – but Sherlock also jumped. His fall was broken, however, by a handy rubbish truck parked outside the hospital. Crucially, John can't see the moment of impact.

Or … Moriarty's body remained on the roof and Sherlock jumped into the rubbish truck, before arranging himself on the pavement with some blood from Molly. John was prevented from taking his pulse by one of Holmes' stooges.

Keeping up? Good. Time to muddy the waters further. John was very disorientated: was that just a result of being knocked over – or might he have been given a shot of the suggestability drug from last week's Hound of the Baskervilles episode? Was Mycroft involved? Might he even have fed Moriarty information about Sherlock in order to engineer such a showdown?